Apparatus for burning portland cement.



T. A. EDISON. APPARATUS FOR BURNING PORTLAND CEMENT. uruonron PILBD00T.24,1906. 7 930,946, V r A A I Patented Aug. 10, 1909.

3 SHEETS-SHEET 1.

, 1n: NORRIS PEYERS 4:0,. mom-Mmevv wAsnmcm T. A. EDISON. v APPARATUSFOR BURNING PORTLAND CEMENT.

APPLIUATION I'II IED 0O'l.24. 1906.

mm W MM a MN m m w f n45 Mowers PUERS co..:=uwm.mm. WASNIIIUHIN. u c,

APPLICATION FILED 001224, 1906.

9 .& H W or mu zkfl 0 A 3 u m 1 LM v m P 3 w IS F ERS ca. mmmyru THOMASA; EDISON, OF .LLEWELLYN PARK, ORANGE, NEW JERSEY.

, arrana'rirs ron nnnnme PORTLAND CEMENT.

Specification of Letters Patent.

Application filed October 24, 1906. Serial no. 340,299.

To all whom it may concern:

Be it known that I, THOMAS ALVA EDISON,

Y acitizen of the United States, residing at Llewellyn Park, Orange,county of Essex,

*andState ofNew Jersey, have invented certain-new and usefulImprovements in Apparatus for Burning Portland Cement, of

I which the following is a descri tion'.

upper end.

In my Patent No. 802,631, atedOctober 24th, 1905, I describe and claiman improved rotary kilnfor burning Portland cement and which I have usedin practicewith excellent results, both as to quality .of product andgeneral fliciency. The said kiln consists essentially of a very longcast iron cylinder, lined with firebrick, the length, being about 150feet and the internal diameter from 5 to 5% feet, one or more streams ofpulverized fuel being n ected into, the cylinder near its lower end, andthe products of combustion escaping through a stack at (the,

he conditions of operation in a rotary cement kiln are greatly opposedto efficiency of fuel,-for the reason that the body of materialundergoing treatment occupies only a small portion of the area of thekiln, so that enormous losses are incurred in the exit gases, whichleave the kiln at a high temperature. Other losses are incurred byreason of the ineffective heating of the material -since practicallyonly a small pro Sortion of the surface of the load of material issubjected to the heat notwithstanding the turning movement given byprojection from -the lining, as has been proposed. Additional losses arealso due to dissipation of heat'by conductionand radiation through andfrom the kiln walls. Furthermore, the fia'me derived from the combustionof pulverized coal is, for its greater part, nonluminous and hencepractically non-radiant, so that in passing practically unconfinedthrough the tubular flue which the kilnpresents, very poor conditionsare offered for.

imparting heat -to the material except in the lowermost part of thekiln, where the flame is luminous and .hence can impart its heat to thematerial by radiation,

The ineffective character. of a rotary cc.-

,ment kiln is made clear by comparing the same with a blast furnace inthe lower end of which the temperatureis higher than in a as low as 4'00degrees Fahr. The reason for this high efliciency in a blast furnace isthat in contact with the material passing downward through the same, sothat the material will be heated by direct impingement, and,consequently, practically all of the heat will Patented Aug. 10, 1909.

be conserved. On the ot er hand, in a modern rotary cement kiln, thematerial occupies but a very small part of the heating chamber, so thatto raise the, material to the higlr tem erature necessary involves theburning of relatlvely enormous quantities of coal, the bulk of whoseheat value is practically wasted. In my said patent, I point out that bymaking the'kilnabout 150 feet in length, without materially increasingthe diameter, so that the ratio of length to inter-.

nal diameter is about 30 to 1, instead of about 12 to 1, as wasthe'practice before my invention and is still very extensivel thepractice in this country, and by large y increasing the load of materialin transit..

through the kiln, it becomes possible to effect material economies inthe cost of fuel, since considerable heat from the combustion gases willbe absorbed by contact with the large load of material in transit towardthe clinkering zone, and substantially all of the carbon dioxid will beevolved before the coin-.

bustion zone is reached, so that the fuel will belburned to the bestadvantage. From my own'observation in the art, I'believe that the kilnwhich I describe and claim in said pat-- ent marks the highestefliciency that can be obtained in apparatus of this general type, sothat if greater eliiciency is to be secured, it must be either in aradically different apparatus, or by the addition of other features ofconstruction. Apparently, the high cost of labor and the low cost offuel in this country must, for a long time, limit the cementmanufacturer to apparatus of the rotarytype, and with this fact in mindI have endeavored to effect further economies in such apparatus by theuse of additional devices, by which a substantially new mode ofoperation is performed.

Briefly stated, what I propose to do is to shower the dry unburnedmaterial or chalk diametricallyacross the kiln as the materialprogresses slowly towardthe lower end, so that "the very hot products ofcombustion passing through the kiln will encounter the incoming materialin the most effective man nor, to thereby heat the same. and drive offpermitting absorption of heat therefrom by radiation, and directcontact. v

While-itwould probably not be feasible in a substantially-horizontal.kiln to'realize the ideal conditions presented'by a vertical blastfurnace in which the entire bulk of v the material is directly acted onat all times by the products of combustion, yet, it is possible' byequipping the kiln with effective showering devices, to maintain morethan 50 per cent. of the material in the path of the products ofcombustion so as to be heated 'rect impin ement. I propose in fact tomaintain at a times within the kiln a. cloud or shower of materialoccupying the entire bore thereof for a considerable length (say for 50.feet, commencing say ten feet from the upper end, in a kiln 150 feetlong so,

- that there will be no' portion of the ore through which the roducts ofcombustion may pass, where suc products will not be in direct contactwith the pulverized. material. In this important respect my presentimprovements are distinguished from the prior suggestions of providingthe kiln with ribs or projections w the material a turning movement andcarry scarcely any of'the material much beyond thehori'zontal axis ofthe kiln. fWith such prior suggestions, even if. the material werecarried as far" as the vertical axis substantially half of the borewould be unoccupied by the material, so that the products of combustionwould be free to pass through the unoccupied Space in a non-luminouscondition and with the heat losses referred to Of course with such aprocedure as I suggest, there would be a prohibitively large loss ofchalk carried away with the escaping gases, unless provision were madeto recover the same, and for this purpose I'make use of an improvedsettling chamber and filter, in which substantially all of the solidmatter escaping with the products of combustion will be separatedtherefrom, so that no loss from. this causewillbe experienced. Such asettling chamber and filter might be conveniently used with any rotarykiln in which the dry process is employed, because even when the chalkis fed along the bottom of the kiln in the old Way, considerablequantities of .it are sucked up by the gases and escape through :thestack. Having obtained a very perfect settling chamber and filter,adapted for the effective separation of any solid or dust-likema tterfrom the products 1ch at best merely give.

seriously affect the character t he resulting clinker.

of combustion, I prefer to use the same in an apparatus-inwhich thechalk is showered instead of turned as explained, through the kiln,since in that way I more effectively heat the material and heat from theesca ing gases.

, A settling eham er and filter suitable for use in combination orconnection with a rotary kiln should have as a .most importantconsideration, a fixed and constant porosity, to thereby present anabsolutely uniform resistance to the draft passing through it, so as notto disturb the correct operationwithin the kilrtitself, since variationsin the draft and quality of 7 Such a 'settlingchamher and filter shouldalso be capable of being effectively cleaned to permit the separatedchalk to be recovered and it should also be of such construction as notto be'afiectedby the high-temperatures encountered in its use.'

also abstract more To this end, the improved settling chamber .andfilter which I have invented and which I propose to herein claim, incombination with a rotary cement kiln, and particularly in combinationwith a rotary cement kiln in which the chalk is showered across thedraft, comprises 'a suitable chamber havin more walls orpartitionsthrou' h which the draft passes, formed of pulveru entorgranular material, presenting innumerable minute tortuous channels,through which the products of combustion find their way, and by whichthe chalk or other solid matter carried therewith, will be separated.

Provision is made for elfecting a slow movement either continuous orintermittent, of the granular material constituting the filteringmedium, so that the filtering medium ,is constantly undergoing change,to permit that portion of the chalk deposited Within the same to beseparated therefrom, as I wil. hereinafter describe and claim. By thuscontinuously changing the filtering medium it cannot become clogged bythe accumulation of the fine material or chalk therein so that itsporosity remains unaltered and consequently its resistance to the draftwill be always constant so as to not affect the conditions within thekiln. In addition to the filtering medium, I also provide a'settlingchamber of suflicientcapacity to permit the velocity of the draft to bevery greatly reduced, so that the lar er bulk of chalk or dust will beseparated y gravity. The chalk so separated from the draft may bereturned directly to the kiln or passed to a suitable stock house andmixed with fresh material, and from which it may be withdrawn whendesired whereby a part of the heat will be thus saved. The filtering medium which I employ is any suitable relarange conveniently between andof an inch. such as coarse sand or coarsely one or' oeopec .3

pulverized cement rock. This material is caused to assume the form of asubstantially verticaLscreen or partition, through which the draftpasses as explained, and which is is separated and returned to the stockhouse,

or elsewhere, while the coarse material-is again returned for use in thefiltering appa-- ra'tus. .Thus, a substantiallyconstant load of coarsefilterlng mater al 18 malntalned 1n transit from the bottom oft-hefilter through the screening'device,-and thence to the upperend of thefilter,- all as I will fully hereinafter describe and claim. p Theobjects of my invention are the fol- .1owing: Iirst:' to provide andproduce an 1m. roved screening device of'consta'ntfporosity, adaptedparticularl for use in combination with a cement in u, but capable ofuse in other connections, and by which a' uni: form resistance will atall-times be imposed to the passageof a draft through it, therebyeffecting. the separation of any solid dustlike particles carried by thedraft, the filtering medium being continuously or intermittentlyreplenished without affecting the peesage of the draftthrough the same,thereby permitting the separated dust-like material Second: to provideand;

to' be recovered. p produce an 'rmproved rotary cement kihi'mcombination w th a filtering device, preferably of the type indicated,and by which any chalk carried out of the kiln with the draft will berecovered, so as to preventloss from that source. Third: to provide an1mproved rotary cement apparatus in which I am enabled to shower thechalk crosswise through the draft in' the kilnin contradis: tinction toa mere turning movement, to

most effectively heat the chalk and to ab stract heat from the productsof combustion,

and at the same time to prevent loss of madinally along the same. Fig.2, a 'longitw diual sectional view on an enlarged scale, showing theupper end of the kiln and the filter. Fig. 3. a cross sectional view onthe line 3----3 of Fig.2. Fig. 4, a plan andseciron sections, itstotal'length being .erablyln the neighborhood of 150 feet, and vitsinternal diameter about 5 or 5!,- feet.

tional View on the line 4 1 of Fig. 2. Fig.

5, a section on the line 5--5 of Fig. '1. Fig. 6, an enlargeddetailsectional view, showing a part of one of the filter walls. Fig, 7, anend view showing a detail of the lowei end of one of the elevators andconveyors leading into the same, and Fig. 8, a section on the line 88 ofFig. 2.

In all of the above views, corresponding parts are represented by thesame numerals of reference.

The kiln 1 as heretofore, is made of cast pref- The kiln is supported onrollers 2, and is maintained at a sl ght angle so as to cause the finematerlal or chalk to progress slowly along the same as the kiln isrotated. The

lirebrick lining 3, is ofthe usual constru'clion, and protects thecast-iron walls from the heat. .The upper .portion of the kiln,

say,- for a length of about 50 feet, is formed of sections 4-4, somewhatlarger in diame-- for than the main portion of the kiln, and

within these enlarged portions I provide inclined wmgs 5 .(see Fig. 5)'arranged to form pockets for-carrying up .the material and shower1ng-1tdiametrically across the kiln; as-will'be understood, whereby thematerlal w1ll -be constantly falling off o f-th e w1ngs,'unt1 l' thewings 'havepassed considerably beyond the vertical line of the kiln,

as shown in saidfigure, so as to maintain a 'cloud or shower of the finedust filling sub.-

stantlally the entire bore of the kiln. In

this. way no unoccupied space is.- offered through which the products ofcombustion may pass .in a non-luminous'con'dition but the products of icombustion will be ofnecessity brought into direct contact with the'fine material. These'wings are made prefera'bl'y 'of firebrick and theirinner'edges'extend substantiallyin line with the bore of the mainportion of the kiln, so that in each of the outer sections 4, additionalspace is provided in which a considerable load of material mayaccumulate to more effectively abstract heat from the products of combustion. By providing additional spaces in this way within the kiln it ispossible to in-,

crease the load of chalk which may be showered by the wings 5, so that50 per cent. or more of the load may be maintained at all times in thedirect path of the products of combustion and'filling substantially theentire bore of the kiln. In this way the flame is made luminous sothatthe heat 'or cement.

stack 7 having a damper 8 therein, so that if desired, the products ofcombustion may pass up through the stack. The stack may also be usedwhen the kiln is first fired or in caseof accident to the filteringapparatus. The pulverulent material or chalk is supplied to a bin 9, andis fed therefrom into the upper end of the kiln by a screw conveyor 10,as heretofore.

'Adjacentto the upper end of the kiln is the settling chamber or filter11, comprising generally a rectangular structure, whose walls may beconveniently built of firebrick I Near the front of the filter is thewall 12, through which passes a flue 13, connecting with the chamber (3,whereby the products of combustion, etc. from the kiln will be directedinto the central part of the filter. Extending longitudinally of thefilter between the wall 12 and the rear wall are two vertical rows ofplates 14, inclined at. a very acute angle (see Fig. 6) and madepreferably of firebrick or cement. I supply to the two sets of plates aload of relatively coarse material, c'onstituting a screening orfiltering medium, and which maybe composed of coarse sand or gravel orcoarsely ground cement rock, the particles ranging preferably between l/16 and 1/8 of an lIlCll in size, the thickness of the body of coarsematerial being about one and one-half inches. The filtering materialwill accumulate between the inclined shelves, so as to material drawnoff at the bottom of'each suitable type,

partition and carrying with it the load of se arated chalk or dust isdeposited b the roller feed 15, onto a conveyer 17 0 any and by which itis conducted to an elevator 18 (see Fig: 7) and is elev coarse materialswill be returned to the vated b 1 the latter and deposited upon a series0 screens 19, provided with checking shelves 20, so as to, prevent thematerialfrom passing too rapidly over ,the screens. By means of thescreens 19, the fine dust or chalk will. fall into a chute 21, whilehtheoppers 16 and be distributed through the latter by conveyers 22. Thepresence of the coarse material intermlxed with fine dust or chalk willvery materi lly facilitate the effective screening of the atter. Fromthe chute 21,

thefine chalk is deposited in the path of the conveyer 23, which leadsto a suitable stock house 24:. The conveyer23, extends longitudinallyof'the main portion of the filter through the agency between the twofiltering partitions. This portion of the filter is formed with aninclined bottom, I as sliQWn,land ccnstitutes a settling chamber whichis of such a size relatively to the area of the kiln that thevelocity'of the products of combustion is materially arrested, so thatthe greater proportion of dust or chalk carried therewith will depositby gravity in the her and be carried off by the conveyer 23 into thestock house. The draft, after passing through the filtering walls,escapes through two vertical openings 25 in the wall 12, and is suckedout from the front of the filter by a fan 26, operated from any sourceof power, preferably an electric motor conltrplled by the kiln man atthe front of the 1 n.

By creating the draft within the kiln of a fan operated by a readilycontrollable motor, the draft is under much better control than whencreated by the stack, as is now the practice, and it may bequicklyvaried by the kiln man to meet any changing conditions within thekiln. It will be obvious that this suggestion of utilizing anartificially created controllable draft within the kiln, can beeffectively employed in kilns of ordinar construction, as well as withkilns of the type disclosed in my patent, and that the expedient is notnecessarily limited to an apparatus of the special .type disclosedherein The hoppers l6 extend, as shown, beyond the partition 12, and areformed with openings 27 therein, so that any surtplus of coarsematerial'fed longitudinally o the hoppers by the-conveyers 22 will bedeposited in the path of the conveyors 17, and thence kept 1ntransit'over the screens 19, and back to the hoppers. In,this way, Iinsure a constant supply ofunaterial to the filtering walls, so that auniform load of coarse material will be always in position on theinclined shelves 14. This is of the utmost importance when the device isused in connection with a rotary kiln, because I am thereby enabled tokeep-the porosity and resistance of the filtering device absolutelyuniform, so as not to result in disturbance in the operation of thekiln. Preferably, checking shelves 28- are arranged in the chamberformed between the front walls 'for the coarse material falling from theopenings 27 onto the conveycrsl'i. V

In operation", the fine material or chalk is fed to the kiln in theusualway and in passing slowly through thesame will enter the pocketsformed by enlarged sections 4 of the kiln, so as to accumulate thereinin opmparativelydarge loads. Within -these pocketsrthe material willbeengag'ed by the wings 5 andcarried upwardly so as to be showereddiametrically across the kiln and settling chamtions. since properlyarranged and shaped directly across the draft. By properlyproportioning-the angle of the wings 5, this showering of the materialcan be adjusted so as to take place even after the wings have passed thecentral vertical line of the kiln, whereby the'boreof'the kiln will besubstantially occupied with a cloud ofnfine particles falling throughthe same and across the path of the draft.. It is not absolutelynecessary to employ the enlarged secprojections might .be carried by thelinmg of-a kiln having substantially-a continuous of combustion.

-veyer' 23.

bore, but such enlarged sections are desirable as they permit largeloadsof the fine material to accumulate therein, and thus allow a much largermass ofmaterial'to be presented to the direct effect of theproducts Bythus showering the chalk across theikiln, it will be very perfectlyacted upon by the products of combustion and nearly all of the heat willbe absorbed by the material, so that the operation may-be made ver reconomical. Such procedure as this would, however, be prc hibitivelycostly, unless some means were provided to se )arate the fine chalkwhich would be earned out of the kiln by the dra ft; and this separationwith my improved apparatus is effected by the settling chamber andfilter. 7

From the kiln the draft carrying with it a relatively largeproportion'of the fine dust, enters the settling chamber between the twofilter walls. The area of this settling chamber is sogreat that thevelocity ofthe draft will be greatly reduced, so that a large portion ofthe chalk will bedeposited by gravity in the settling chamber and'willbe carried off into the stock house'24' by the con- From the settlingchamber the products of combustion pass slowly through the channelspresented by the granular filtering material carried by the inclinedplates 14, the areapresented by the filtering material being veryextensive and permitting the products of combustion to seep relativelyslowly through the filtering walls. I By thus causing the products ofcombustion to pass slowly through the fine channels or pores presentedwithin the filtering material, any excessively-fine dust-like solidparticles carried by the draft and which were not deosited in thesettling chamber will be ef- .eqtively separated and retained within thefiltering material on account of the slow movement of the gaseouscurrents in the channels, and also because the channels are sotortuousthat the dust particles must in many cases be lifted up againstgravity,

' which the slow movement of the gaseous currents is unable to effect.

Preferably, I maintain the load of coarse particles in constant but veryslow movement, so that the filtering body 1s being "constantlyreplenished, while at the same time its porosity remains unchanged. Amovement su'flic'ent to effect a complete change of the filtering wallin one hourwill be sufficiently rapid forthe purpose. Although thefiltering material. thus in constant movement, the resistance offered bythe filtering walls ren'iainsconstant so that the draft within thekiln'may be always maintained inrthe most effective condition withoutbeing subjected to objectionable fluctuations. r

I am aware that 111 some of the industrial arts it has been proposed tomake use of filtersfor separating fine dust-like particles from gaseouscurrents, for example, by equipplng a'settling chamber with a bottomformed of a series of bags through which the draft escapes leaving adeposit of the Jfine material within th'filter bags. But

with such a device, as with all forms of fil ters with which I amfamiliar, the porosity of the filteringmedium is'gradually lessened bythe accumulation of the separated material within its pores and conseuently, the resistance to the passage of t e draft is greatly increaseduntil tie draft finally becomes choked'. Such an arrangement could notbe effectively used in connection with a cement kiln, because it isessential for the correct operation of such a kiln that the conditionsof the draft-should bekept uniform at all times and'controllable.

Having now described my invention, what I claim as new and desire tosecure by Let ters Patent is as follows:

1. In cement burning apparatus,-the combination with a rotary kiln,means for burn-' ing material in transittln-ough the same, and mea'nsfor showering the material diametrically across the. kiln and directlyin the path of the products of combustion, of a settling chamberconnected with the discharge from the kiln, and of large size to permitthe velocity of the products of combustion to be very greatly reduced soas to effect a separation bygravity of the solid or dust-like particlestherefrom, and a filter adjacent to the settling chamber and throughwhich the products of combustion pass from the settling chamber toeffect a final separation of the finer solid'ordust-like particlescarried in suspension, said filter presenting at all times a constantporosity, substantially as and for the purpose set forth.

2. In cementburning apparatus, the com: bination with a rotary kiln, andmeans for burning material in transit through the same, of a settlingchamber of large size to reduce the velocity of the products ofcombustion and effect a separation by gravity of the dust-like particlestherefrom, and a filter having at all-times a constantporosity andthrough which chamber and filter controllable exhaust fan connected withthe same, of a settling chamber connected with the discharge from thekiln, the op osing Walls of said settling chamber being ormed of loosegranular material and each Wall constituting a filter, and meansfor-admitting the discharge gases from the kiln betweenthe said Wallssubstantially as and ,for

the purpose set forth; 4. In cement burning apparatus, the combinationwith arotary kiln and means for burning material in transit .through thesame, means for showering the material diametrically across the kiln anddirectly "in the path of the productsofflcombustion, of

a settling chamber-connected with the discharge from the kiln theopposing walls of said settling chamber formed of loose granularmaterial and each wall constitut showering the pulverized materialtherein.

diametrically across the kiln and directly in the p th of the roducts ofcombustion, of'a setting chamber connected with the discharge from thekiln, vided with surfaceson by gravity, and means for removing the same,and filtering walls, and means for automatically collecting and removindust deposited in the same, substantiafi described.

This specification signed and witnessed this'22ndday of October 1906. I

' THOMAS A. EDISON.

said chamber proyas \Vitnesses:

FRANK L. DYER, ANNA KLEHM.

which dust deposits the v

